In current semiconductor industries, the products of the integrated circuit (IC) devices can be roughly divided into three types, including analog circuits, digital circuits, and mixed signal circuits. Memory devices belong to one important type of the digital circuits. In recent years, the development of flash memories is particularly rapid comparing to other types of memory devices. One advantage of the flash memory devices is the ability of storing data without applying external electrical power. Therefore, a flash memory device can be used as a nonvolatile rewritable data storage for storing data that can be maintained when the external electrical power is disconnected. In addition, the flash memory devices have many other advantages, such as high integration level, fast data-storing speed, good erasability and rewritability, etc. Therefore, the flash memory devices are widely used in many fields including the micro-electro-mechanical systems (MEMS), the automation controlling systems, etc. Thus, how to improve the performance of the flash memory devices and how to reduce the product costs of the flash memory devices become very important for research.
NOR gate erase through oxide (ETOX) flash memory device is one type of flash memory device that has excellent features. The structure of an NOR gate ETOX flash memory device can include a gate structure on the surface of a substrate, and a source region and a drain region located on both sides of the gate structure respectively. The gate structure may include a tunneling oxide layer on the surface of the substrate, a floating gate layer on the surface of the tunneling oxide layer, an insulating layer on the surface of the floating gate layer, and a controlling gate layer on the surface of the insulating layer.
Performances of various kinds of electronic devices are improving as the development of the high density flash memory technology. For example, the flash memory devices are used as data-storage devices in digital cameras, laptops, tablets, and other electrical equipment. Thus, reducing the size of the flash memory cells and reducing the costs of manufacturing flash memory devices may be challenges for current technology development. As for the NOR ETOX flash memory devices, a self-align contact fabrication technique can be used to form the conductive structures on the surfaces of the source region and the drain region to satisfy the requirements for forming smaller-sized flash memory devices.
However, the existing fabrication process for forming a flash memory device is complicated and the performance of the flash memory devices may still have defects.